The stunning domed pink sandstone residence of India's President Pratibha Patil today became the first home to be counted as the world's biggest census got underway.

The exercise to count the estimated 1.2 billion population and record such varied data such as internet use and clean water provision will involve 2.3 million census-takers, or "enumerators," travelling across more than 630,000 villages and over 5,000 cities in the country to visit every structure that serves as a home.

Computer and mobile phone ownership has been added for the first time.

From exclusive apartment blocks in Mumbai to remote rural villages, the 11-month exercise will create a comprehensive picture of modern India — and modern Indians.

The census-takers also plan to include millions of homeless people who sleep on railway platforms, under bridges and in parks.

"It is for the first time in human history that an attempt is being made to identify, count, enumerate and record and eventually issue an identity card to 1.2 billion people," the home minister, Palaniappan Chidambaram, said.

India conducts a national census every 10 years. Census-takers are typically government officials, school teachers or other local officials who go home-to-home collecting data on the size of families, marital status, education and work information. For the first time, they will also count bank account holders and cell phone users.

Many state governments have launched publicity campaigns to encourage participation.

In the poor eastern state of Orissa, street plays by local dance groups about the census were being organised in all district headquarters and adverts run on local television, Bishnupada Sethi, director, census operations, Orissa, told reporters. 'All district collectors have also been requested to arrange marathons, cycle rallies using banners and poster and debate competitions for school children,' Sethi said.

States have an interest in having all their population counted as the totals can influence the allocation of central funds.

While China, the world's most populous country, also counts its population, its census is carried out by various agencies, including Communist party units, commune leaders and factory heads, unlike the single New Delhi-based Registrar and Census Commission that carries out India's count.

India's census will face a special challenge from leftwing extremists active in 20 of the country's 28 states who have stepped up a campaign of violent attacks on government officials. There have also been demands for the census to include caste, the strict social hierarchy that traditionally determines an individuals place in society. Advocates say a true picture would allow more effective affirmative action schemes to be implemented.

The census-takers plan to finish their work by February 2011.

India has held a census every decade since 1872 when under British colonial rule. The cost of the latest is estimated at more than £650m and will consume at least 11m tonnes of paper.